1. Field of the Invention
This invention relates to neural tissue stimulation and infusion techniques, and more particularly relates to such techniques for treating movement disorders by stimulation of and/or drug infusion into the pedunculopontine nucleus (PPN).
2. Description of Related Art
Patients with neurodegenerative diseases or trauma like cerebral infarct or spinal cord injury can have a variety of movement and muscle control problems, like resting, postural, intention or action tremor; dystonia (improper muscle tone); spasticity (undesirable movements, or muscle co-contraction); dyskinesia (poorly executed movements) or involuntary movements like ballismus, choreiform movements and torticollis (inappropriate movements or limb control). Many of these problems can be called hyperkinesia. Although they can be chronic, or worse, progressive, they also may have times of relative remission. Such problems are found, at certain stages, for patients with Parkinson""s disease, multiple sclerosis, cerebral palsy, secondary to deafferentation pain, post stroke, post apoplexy or anoxia, post head or spinal trauma, post poisoning, cerebellar disease, etc. Dyskinesia also may result from long term usage of levodopa or other drugs, especially for Parkinson""s patients.
A number of techniques are used for treating these and other movement disorders. Electrical stimulation and drug infusion techniques have become increasingly popular. In the case of electrical stimulation, an electrical lead having one or more electrodes is typically implanted near a specific site in the brain or spinal cord of a patient. The lead is coupled to a signal generator which delivers electrical energy through the electrodes to nearby neurons and neural tissue. The electrical energy delivered through the electrodes creates an electrical field causing excitation or inhibition of the nearby neurons. For example, stimulation of the vagus nerve as described in U.S. Pat. Nos. 4,702,254; 4,867,164; and 5,025,807 has been used to reduce the likelihood that a person with epilepsy will experience a seizure. For example, U.S. Pat. No. 5,716,377 entitled xe2x80x9cMethod of Treating Movement Disorders By Brain Stimulationxe2x80x9d discloses techniques for stimulation of various portions of the brain.
These techniques, however, may not be as effective in the treatment of certain movement disorders such as akinesia and gait disorders for certain patients, and balance and walking disorders and many other symptoms that are resistant or are inadequately treated by current techniques. In addition, side effects of these therapies may limit the application of these techniques, for example, due to cognitive side effects, visual disturbances, speech disturbances and depression associated with these therapies. Further, these techniques may lose their effectiveness over time, sometimes due to degeneration of neurons, such that the patient may no longer respond to the treatment therapy in the certain portions of the brain, such as the thalamus, the globus pallidus, or the subthalamic nucleus. Other times, the treatment therapy may not be as effective to adequately alleviate a symptom of a movement disorder. Accordingly, there remains a need in the art to provide a treatment technique that directly targets neural tissue that handles motor control.
A preferred form of the invention uses electrical stimulation of the PPN to treat a movement disorder. The treatment is carried out by an implantable signal generator and an implantable electrode having a proximal end coupled to the signal generator and having a stimulation portion for electrically stimulating a predetermined stimulation site in the neural tissue. Alternatively, the treatment may be carried out by an implantable pump and a catheter having a proximal end coupled to the pump and having a discharge portion for infusing therapeutic dosages of the one or more drugs into a predetermined infusion site in neural tissue. By using the foregoing techniques, the symptoms of movement disorders, such as Parkinson""s disease, Akinesia, Bradykinesia or Rigidity, Ballism, Hemiballism, Chorea, Torticollis, Spasticity or Dystonia can be alleviated. In addition to stimulation of the PPN, other portions of the brain or spinal cord may be stimulated to provide more comprehensive treatment therapy. In other embodiments of the invention, drug infusion may be used as treatment therapy instead of or in addition to the electrical stimulation.
In another embodiment of the invention, a sensor is used in combination with the signal generator and stimulating electrodes to treat the movement disorder. In this form of the invention, the sensor generates a sensor signal related to activity resulting from the movement disorder. Control means responsive to the sensor signal regulate the signal generator and pump so that the neural disorder is treated.
By using the foregoing techniques, the symptoms of many movement disorders can be controlled to a degree unattainable by prior art methods or apparatus.